This invention relates to displays for three-dimensional (3-D) images and more particularly to a display using a moving two-dimensional (2-D) projection surface and controlled illumination source.
Use of a moving 2-D projection surface for the display of a 3-D image is well known. The illumination sources for such displays have typically been one or more electron beams deflected by controlled electromagnetic fields and impinging upon a rotating phosphor screen or one or more high power lasers deflected toward a screen by a series of controlled mirrors. A series of points or trajectories (vectors) is displayed by controlling the time-varying deflection of the source beams. As the projection surface sweeps out a 3-D volume, all points in a 3-D volume can be illuminated. Due to the persistence of human vision, if a point is repeatedly illuminated for a brief interval with a repetition period of no more than approximately 1/20 second, the point appears to be illuminated without flickering.
In another technique for projecting a 3-D image, a transparent crystalline material (glass) that produces visible illumination at the point of intersection of two light beams has been used. In a process known as two-step, two-frequency upconversion, the material is excited by light beams at two different wavelengths typically in the near-infrared spectrum. The material has been doped with small quantities of an active ion which is excited by the intersecting beams producing visible light at the points of intersection. (See Lewis et al, IEEE Trans. Elec. Dev. ED-18(9), September 1971, pp. 724-732; Downing et al, Science vol. 273, pp. 1185-1189, Aug. 30, 1996). Mechanical deflection mechanisms control the point of intersection of two light beams thereby sequentially illuminating points in the projection volume to form the image.
Both these displays are complex, expensive, and are incapable of displaying images with very large numbers of illuminated points.